Long chain primary alcohols e.g. C8, C9 and C10 alcohols are widely used for producing plasticisers. For this, the alcohols are reacted with polycarboxylic acids, such as phthalic acid and adipic acid, forming the corresponding esters. Commercially important examples include adipates of C8, C9 and C10 alcohols, for example di(2-ethylhexyl)adipate, diisononyl adipates and diisodecyl adipates; and phthalates of C8, C9 and C10 alcohols, such as di(2-ethylhexyl)phthalate, diisononyl phthalates and diisodecyl phthalates.
Diisononyl phthalates are general purpose plasticisers for polyvinyl chloride (PVC), and are used in almost all known flexible PVC applications, both via plastisols and dry blends. Typical applications include those in toys, films, shoes, coatings, floor coverings, gloves, wallpaper, synthetic leather, sealants, tarpaulins, car underbody coatings, upholstery, foamed mats, and sound deadening panels, all based on plasticised PVC. They are also used for producing PVC cable sheathing and insulation, and other calendered flexible PVC products.
Diisononyl adipates are used especially in films, and at lower levels in other products such as wallpaper, synthetic leather, car underbody coatings, gloves, and sealants based on plasticised PVC. Diisononyl adipates are used in particular when the products are intended to be used at low temperatures and/or when plastisols are used as process intermediates.
GB-A-1,330,112 discloses the use of isononanols in the formation of diisononyl esters of phthalic acid or adipic acid as plasticisers where the isononanols have been prepared from 2-ethyl-1-hexene in a known manner by the oxo synthesis by reaction with carbon monoxide and hydrogen at elevated temperature and pressure in the presence of carbonyl complexes of metals of the 8th transition group of the Periodic Table, if desired followed by hydrogenation. Because of the branched feedstock, the product alcohol does not contain n-nonanol. The 2-ethyl-1-hexene is obtainable by dimerising 1-butene with trialkyl aluminium compounds. The diisononyl esters described are said to be suitable plasticisers for polyvinyl chloride and to have low volatility, low viscosity and to give good low temperature resistance in the polyvinyl chloride compositions plasticised therewith.
U.S. Pat. No. 4,623,748 describes dialkyl adipates, inter alia diisononyl adipates, prepared by reacting propylene oligomers or butylene oligomers from the dimersol process in the presence of supported tantalum (V) halide/oxide as catalysts, reacting the resultant C8, C9 or C12 olefins to give C9, C10, or respectively C13 alcohols and esterifying these alcohols with adipic acid. The dialkyl adipates are said to have high flash points and to be suitable for use as lubricants.
GB-A-1,114,379 discloses an isomeric nonanols mixture which comprises n-nonanol and includes essentially no alcohols having more than one branch in their carbon skeleton. The mixture is prepared by hydroformylating an octene fraction obtained by polymerizing ethylene with trialkylaluminium catalysts and reducing the hydroformylation product.
WO 92/13818 describes the preparation of diisononyl phthalates starting from butenes and where appropriate, from olefin mixtures comprising propene. The starting materials are oligomerised over supported phosphoric acid catalysts at reaction temperatures of from 200 to 235° C. to give essentially octene-containing olefin mixtures. These octene-containing olefin mixtures are hydroformylated and subsequently hydrogenated to give essentially alcohols mixtures comprising isononanols. These isononanol containing alcohol mixtures are esterified with phthalic anhydride to produce ester mixtures essentially comprising diisononyl phthalates suitable as plasticisers for PVC.
U.S. Pat. No. 4,291,127 describes phthalates of C9 alcohols obtained by an oxo reaction of C8 olefins, hydrogenation of the reaction product and esterification of the C9 alcohols using phthalic anhydride. From 3 to 20% of the C8 olefins have an isobutene skeleton in each molecular chain and less than 3% of the olefins have a quaternary carbon and also more than 90% of the total amount of the C8 olefins are present in the form of n-octenes, monomethylheptenes and dimethylhexenes. The C9 alcohols contain from 2 to 6 wt % n-nonanol. The C9 phthalates are intended to be suitable as plasticisers for PVC.
EP-B-0278407 describes a C9 alcohol mixture for the manufacture of plasticisers which comprises certain proportions of components with a specified GC retention behavior in relation to certain reference compounds. Plasticisers based on the C9 alcohol mixture are intended to give advantageous resistance to low temperatures and good electrical insulation properties.
U.S. Pat. No. 6,355,711 describes plasticiser esters prepared from a C9 oxo alcohol mixture which is 6% straight chain, 74% mono-branched, 20% dibranched and less than 1% tri-branched, the alcohol being derived from an olefin having at least 50% methyl branching at the beta carbon atom.
U.S. Pat. No. 6,437,170 describes mixtures of isononanols and their diesters of adipic or phthalic acid which have defined area signal ratios in the 1H NMR spectrum. Reference to isononanols relates to mixtures that are low in unbranched materials.
WO 03/029180 relates to phthalic acid dialkyl ester mixtures including dinonylphthalate isomer mixtures whose viscosity is controlled by the composition of the isomerically pure alcohols from which the mixture can be made. The tables in WO 03/029180 set out several different blends of nonanol isomers and the viscosity of the diisononyl phthalates produced from the different blends.
The Journal of Chromatography, 16 (of 1964) on page 216, describes two C9 alcohol mixtures containing respectively 36 and 24% of linear alcohols, the balance being branched molecules, of which 53 and 34% respectively of the branches are methyl branches.
Since their introduction in the middle of the 20th century, esters of branched C9 alcohols have gained widespread use as plasticisers for PVC. PVC compounds prepared with phthalate esters of branched C9-rich alcohols are used in many different market segments; these include electrical wire insulation, flexible vinyl flooring, vinyl coated wallpaper, vinyl shower curtains, synthetic leather, vinyl boat covers, vinyl swimming pool liners, vinyl stationary products such as notebook covers, and tarpaulins.
Esters of branched C9-rich alcohols are preferred over esters prepared from 2-ethylhexanol, because when used in PVC compounds the C9 esters yield performance advantages over the pure C8 esters in improved extraction resistance to water, lower emissions during processing, lower specific gravity and improved low temperature flexibility. However these products require 1 to 3 degrees C. higher processing temperatures and slightly longer dry-blending times than comparable products based on the pure C8 esters.
In accordance with Wadey et al, “The Nonyl Phthalate Ester and Its Use in Flexible PVC”, Journal of Vinyl Technology, December 1990, Vol, 12, No 4, pp 209-211, there are currently known dinonyl or di-2-methyloctyl (alpha branched) phthalate esters, which are not yet commercially available. Other commercially available phthalates vary in their degree of branching. These include moderately branched phthalate esters (Jayflex® DINP); slightly branched esters (Palatinol® N, Vestinol® 9); highly branched esters (3,5,5-trimethyl-hexyl phthalate type); and linear C9 phthalate esters (Jayflex® L9P, 70% n-nonyl, 30% various alpha branched disomers).
Although the C9-rich esters offer advantages over the pure C8 esters with lower emissions, the level of emission is often not acceptable for some end-users. For products used in the interior passenger compartments of automobiles, manufacturers often develop specifications for the maximum level of emissions which can be released as the automobile sits in the sun. These emissions can result in the development of a “fog” or “light-scattering-film” that condenses or forms on the inner side of the windscreen. Currently no pure C8 phthalate esters and no branched C9 phthalate esters can satisfy the specifications which require a maximal fog formation observed after 3 hours at 100° C. in a fog testing apparatus. To meet these performance criteria, phthalate esters of branched or linear C10 and C11 alcohols or phthalate esters based on the more expensive linear C9 alcohols (such as Jayflex® L9P) or esters of trimellitic anhydride are used.